A representative for Advent declined to comment.

Despite the change, Advent received interest for $18 billion against its $12 billion target, the people said.

EQT, meanwhile, exceeded the initial 5.25 billion-euro target on its latest fund to reach 6.75 billion euros, to satisfy demand from backers, according to a person familiar with the matter. The fund was oversubscribed and more than 70 percent of commitments were from repeat investors, the firm said at the time.

Strong Performance

Advent joins Warburg Pincus and Hellman & Friedman in choosing to raise funds without a hurdle. But investors will only let them do it if the fund’s performance is consistently strong, according to Mounir Guen, the chief executive officer of MVision Private Equity Advisers, which counsels firms on fundraising.

“The second returns drop, a hurdle will be in the next fund,” Guen said.

KKR & Co., one of the world’s biggest buyout firms, is proof of that. The group added the mechanism to its most recent North American and European buyout funds after pressure from investors, said people familiar with the matter. Its 2006 European fund is set to return 50 percent more than backers’ original commitments, well below the 150 percent managers were aiming for over the same period.

A spokeswoman for KKR declined to comment.

No Fees

Investors used to wield their power more fiercely. Three years ago, Apollo Global Management LLC agreed to give investors all the transaction fees levied on companies in its flagship pool, after first proposing that they would get an 80 percent share.